If you put your suspect HD into someone else's PC, make sure you set it as "slave" (on the jumpers, which will almost certainly be labelled telling you how to do that) do it doesn't try to boot from your HD in his PC.
Also, make sure the PC you put it into has very good virus protection (eg AVG) and as soon as you've booted up, scan your HD with that before you do anything else. You wouldn't want to infect the "new" PC with the virus that's on yours.
Or: boot your PC from a bootable Linux CD (eg a Knoppix one). That will allow you to look at the hard drive, and if necessary copy all your important stuff off it (if you don't already have it backed up).